The growth of past, present, and future forests was, is and will be affected by climate variability. This multifaceted relationship has been assessed in several regional studies, but spatially resolved, large-scale analyses are largely missing so far. Here we estimate recent changes in growth of 5800 beech trees (*Fagus sylvatica* L.) from 324 sites, representing the full geographic and climatic range of species. Future growth trends were predicted considering state-of-the-art climate scenarios. The validated models indicate growth declines across large region of the distribution in recent decades, and project severe future growth declines ranging from -20% to more than -50% by 2090, depending on the region and climate change scenario (i.e. CMIP6 SSP1-2.6 and SSP5-8.5). Forecasted forest productivity losses are most striking towards the southern distribution limit of *Fagus sylvatica*, in regions where persisting atmospheric high-pressure systems are expected to increase drought severity. The projected 21st century growth changes across Europe indicate serious ecological and economic consequences that require immediate forest adaptation.

Edurne Martinez del Castillo, Christian S. Zang, Allan Buras, Andrew Hacket-Pain, Jan Esper, Roberto Serrano-Notivoli, Claudia Hartl, Robert Weigel, Stefan Klesse, Victor Resco de Dios, Tobias Scharnweber, Isabel Dorado-Liñán, Marieke van der Maaten-Theunissen, Ernst van der Maaten, Alistair Jump, Sjepan Mikac, Bat-Enerel Banzragch, Wolfgang Beck, Liam Cavin, Hugues Claessens, Vojtěch Čada, Katarina Čufar, Choimaa Dulamsuren, Jozica Gričar, Eustaquio Gil-Pelegrín, Pavel Janda, Marko Kazimirovic, Juergen Kreyling, Nicolas Latte, Christoph Leuschner, Luis Alberto Longares, Annette Menzel, Maks Merela, Renzo Motta, Lena Muffler, Paola Nola, Any Mary Petritan, Ion Catalin Petritan, Peter Prislan, Álvaro Rubio-Cuadrado, Miloš Rydval, Branko Stajić, Miroslav Svoboda, Elvin Toromani, Volodymyr Trotsiuk, Martin Wilmking, Tzvetan Zlatanov, Martin de Luis